Thanks very much! Tomorrow is my maths exam and I'm preparing best as I can. It'll help me, I'm in junior college, still watching this. Helpful video. 🙂
Best of luck! The best you can do now is go over your notes, read through the process on any math you found tricky and refamiliarise yourself with it, doing a couple of examples (probably from some online site like math-aids.com where you can check your answers). Prime factorization is kind of a memory-muscle thing. Once you've done enough of it, you just remember it. I doubt they'll give you numbers big enough to force the use of this method, but I like to be prepared for all eventualities. Usually the factor tree is good enough. To be honest what I do now with a big number is combine the two. So I'll divide until I can spot a value from my tables knowledge, then flick into factor-tree mode and finish it in a couple of seconds. But always circle your primes so you don't accidentally miss any. All the best for your exam tomorrow, I hope it's a walk in the park for you. 😃🤗😎🤩👍💕
You made it so easy to understand. Thank you so much!! I appreciate people like you who take the time to help those who want to learn. Thanks again! :)
Ur way of explaining is very nice i could explain it to my son very nicely thank u please keep making more of such videos n also make a video on data handling stay blessed
For super fast factoring I first notice the 0. So I am taking a 2 and 5 all at once. I also look to grab another 2 or 3 at the same time. In her case I'd first divide by 30 and repeat. Also, checking divisibility by three does not require you have the total. Just skip over the 3,6, and 9 digits. In her example just add 7 and 2. As a matter of fact, while you are doing 3 do 9 at the same time. In that case skip any 9s, but you do need to see that 6 and 3 are nine, and you can group 7 and 2 to be a nine. My first division might have been a 90 in her example.
Oooh, Jim! You're a math-BEAST! I love it! I can spot them, like you, but I definitely feel more comfortable going one at a time, even though I can see what's coming next. Maybe I just need to do a bunch more (as if I have time for that!! lol). I like to get to the point where I can spot a big one, then jump into a factor tree and finish it with a speedy flourish.
Please do yourself a favour and just focus on nailing the prime factorization of a given number. You can get to cube roots at some point in the future.
i love the divisibility rule for 7: double the last digit take rest of the number all digits left of the last digit and use that to subtract your original calculation which is the last digit times two, then check to see if its a factor of 7
You’re very welcome. You can speed this method up even more... when you get to a number you know in your tables, you can switch to factor tree and finish it in seconds! There’s an example of me doing this in one of the vids Finding all the Factors of a Number Using Prime Factorization. 🤗😃😎😉💕
thank you so much! im in eight grad and I never understood this until now, I scored above 90 in my square and square roots test because of this video! thank you :)
Fantastic stuff! And if you like, you could go even faster!!! Here's how... Use the division strategy you learned here till you get a division answer (quotient) whose factors you know. For example let's say you end up with an answer to your division problem as 84. That's fabulous, because from your tables knowledge, you know you get 84 from 7 x 12. So the sprint-cut here is to jump out of division and into factor tree mode, right where you are on the page. Show that 84 as being from 7 x12, and 12 is from 2x6, 6 is from 2x3. Circle ALL the primes, just as every other prime factorization you've done. List them off in ascending order, or even better, using exponent notation, and you just aced it in double-quick time! NICE!!!
EXCELLENT! Now in this video, I'm using short division all the way down to 1. But in fact... you can go more swiftly, IF you want. Let's say you get a big number and you've whittled it down to 144. There's no reason to keep using the division method if you don't want. You know 144 is from 12x12, so you could just flick into factor tree mode if you want... and each 12 is from 3x4, and each 4 is from 2x2! Just make sure you DO circle all those primes at the end, and make sure you collect them ALL for your final statement. If you switch, once you hit a number whose factors you know, you can complete the prime factorization in seconds! Now I hope you do something REALLY cool with this knowledge and totally ACE ANY number your teacher gives you for prime factorization using this little flourish to finish off. How slick is THAT!? I'd LOVE to see your teacher's face, when they see your understanding demonstrated on the page like that!!
Nice! Thanks very much. And actually you can go even faster! The moment you get an answer which you recognise from your tables knowledge, you can flick into factor tree mode and finish it in seconds!
For an easy look at how to think your way to a remainder, take a look in my Division playlist, at the vid called Short Division with a Remainder. I'm teaching this to a grade 3 class next week! Two of them told me they won't be able to do division (I think they've heard about LONG division), but I think they will kill it with short division. I just hope their parents don't tell them it's 'wrong' because they may never have seen it.
@@LetsDoMath Oh my god I have done division all along to find the prime factors now I can find them in matter of seconds I have mastered it thank you. May God bless you
@@acy1335 Ooooh! I LOVE this comment. How come nobody has shown you this yet? Wait... Are you saying you've been using LONG division to do this? If so... eeek! I'm surprised you're still upright! So... yeah, you can use SHORT DIVISION! You can see why it's my preferred way to divide! After doing this vid, I made a couple of others on Finding All the Factors of a Number. In those I just went at it more naturally - the moment you hit a value whose multiples you know, you can switch to the tree method then you can nail those primes in a few seconds! That's the benefit of having a bunch of math tools in your 'toolkit', so you can pull the right one just as you need it. There's always more than one way to solve a problem. If you've only been shown a single way, I feel bad for you, it's not meant to be that way. Well, not in MY opinion anyway. 😉🤗🤩💕
That's GREAT! It may well be that you never get a big number in an exam, but if you do, you're not going to sweat, because you have a strategy! You know multiple ways to do a prime factorization and that is ALWAYS stronger than just 1. Good for you!!
Oh God I just loved it THANKS it's gonna save my 20 minutes which I used to put in my whole exercise whose actual time taking is 5 minutes!! Great !!!! I'VE SUBSCRIBED YOUR CHANNEL ONLY AT THE BASES OF THIS VIDEO HOPEFULLY I THINK IT'S GONNA BE USEFUL FOR SURE AND ONCE AGAIN THANK U SO MUCH😊
Hi there. Glad this vid helped you. Once you've got your head around this, you can speed up even more! When you hit a quotient that you know from you tables knowledge, you can flick into 'factor tree mode'. For example if I got an answer of 96, I know that's the product of 8x12, so instead of writing out another division - and now those are both compound numbers, not prime, now I switch to the tree and show 8 and 12. 8 is from 2 x4, 4 is from 2x2, and I circle those 3 twos. And on the 12 side, I can say 12 is from 2x6, 6 is from 2x3. Here I circle both 2s and a 3. And I can do all that in seconds, as can you. Much faster than continuing to divide by 2 a bunch of times. Cool!
Glad you like it. This method sticks to itself the whole way through. In the vid on finding all the factors of a number using prime factorization, I get a bit more relaxed with it. The moment I get to a number that’s in our tables knowledge, I flick to factor tree mode instead and finish it in a couple of seconds. But you should do whatever feels comfortable to you, and as long as it works, and you and your teacher can understand it, it’s all good. 🤗😎🤩😉
Happy to help, glad you get it now. You can combine this with the factor tree approach if you like, once you get down to a number whose factors you know. That will finish off the prime factorisation in a few seconds.
Hi Laxmi, Thanks for your note. I'm so glad it was easy to understand. It's good to be able to handle anything a teacher or exam can throw at you. It will give you lots of confidence, and that's ALWAYS a great thing. Good for you! 😃🥰🤩
An easier way to determine whether a number is divisible my 7: If the last two digits of the number are in the 7 times table, it is divisible by seven.
I love the idea, but I don't think this is reliable though. I tried 456/7 (56/7=8)... Calc answer = 65.14285714. I am sorry. I wish it was right. It does work sometimes, but not always. To be really honest, the divisibility rule for 7 is so time consuming, it's actually quicker for me to just scribble a division and check. I love how you thought about it and sent me a note. Thank you so much for that. :0)
Oh, If i was one of those 'stealing credit proud rude girls' i would say i thought of it. But sadly, i learnt it at school. Its in our textbooks, too. I think its because i study the CBSE syllabus. but thanks for the quick reply.. i thought i wouldnt get one for like, a few months. Glad to see you're still active!
I am always working on something. On the replies front...YT is set up to send an alert when someone sends me a note. And I always respond, unless it's a rude one, and those I just chuck, because who needs that sort of negativity? The thing is, it has happened a few times that it didn't alert me, and then I only spot the note if I happen to check through a film's comments. Then I feel terrible because I am late answering. So if anyone sends me a note and you don't get some kind of response, please feel free to send me another one. I don't ignore anyone. Have a lovely day. Hope the math goes well. I am heading off to take a grade 7 math class now.
You're welcome 😊 And now I'll tell you about the 'speed-up' you can do. Instead of dividing by primes all the way down to 1, when you get to a number whose factors you know, you can jump into factor tree mode and finish in seconds! Just be sure to still circle all the primes and still gather them all up at the end! NICE!!
It was easy only because you choose a number with those prime factors, if a number, say 'x', is composite then it has at least one prime less then the square root of x, (x^1/2), so take for example 30623 if you tried to factor it, even supposing you knew divisibility test for a lot of primes like 13, 17, 19, 23... (i guess no one would learn divisibility for primes bigger than these) you would still not be able to factor the example that i gave you because you had to check all the primes up to 174, (in fact 30623 is actually 113*271) It's okay that you show a way to factor MOST 5 digit numbers, but a side note on why this doesn't always work would've made the video more useful for the viewers
This is an interesting comment. The process worked easily because I created the number by multiplying up my chosen primes, then I just chose my logical order to extract the primes. I think this is a reasonable thing to do, since at up to grade 8, I don't expect ANY teacher would give an example like the one you came up with. Please remember that this channel is about giving students the power and confidence to do the math, not about showing them that it could possibly be super-tricky and you may find it stumps you completely. They've had enough of that experience already, by the time they find me. The hardest school example I'd expect to be given would end up delivering a prime such as 41, or 59 (a prime under 100 in any case) at the end of the division sequence, and students would be expected to spot that as a prime, not know its divisibility rules. I only ever show what I feel is needed in a video to get students revved up to have a crack - none of my videos is about running to a certain time (my kids tell me 10 minutes is the magic UA-cam earning length). Only what you need, and enough examples so I think students will get the approach and be ready to roll. Thanks for sending me your note. :o)
LadyDMcollector Thanks for clarifying, I tought I could "add" some insight for the ones who have no trouble on this topic, I didn't want to show how It can get tricky, rather I think too many students just learn to do things mechanically without understanding the essence of It... Anyway, thanks for the kind response! :)
I answered this before I saw your comment, but I said basically the same thing. I don't think you'd ever be asked to factor a number like 30623 on a test, but it's good to know how. And it's a MASSIVE amount of work if you're doing it mentally. If you are allowed to use a calculator, it would be very easy because you could divide 30623 by 3, 7, 11, 13, and so on and simply see if the answer comes out even. You would have to have the primes memorized up to 173 in this case. If you didn't, then you'd have to divide by EVERY number ending in 1, 3, 7, or 9 (because those COULD be primes), and it would take longer.
@@jeffw1267 yeah for sure no teacher would "trick" you with such question, but nevertheless no matter how I try I cannot single-handedly improve my school, thus I'd like other resources (such as internet) to provide something more for who Is willing to learn "one step further" my comment was just aimed at giving intuition towards the concept that prime numbers are like "Building blocks" for Natural numbers, (Check "fundemental theorem of arithmetic" for more details), primes are beautyful just like maths in general, there's no such thing as ugly maths but it's teachers fault whom just want you to know that "A Is true", or "Given this follow this pattern of steps and you complete the exercise", good job now you can exit school with your sufficiently high grade having your brain programmed to be able to do those things (until you don't forget them of course), they spend more time forcing the students to learn something than they do motivating the students to study in the first place, Sorry for the very long comment, didn't want to be missunderstood... Greetings ^_^
One more easy trick If you see zeros then cut the number of zeros and add the 2^n*5^n in it's factor. See the below example to understand for ex:- 12500 then two factors will be (2^2)*(5*2) { 2 because there are two zeros} then it becomes 125 which is 5^3 . So all factors will be 2^2 * 5^5
You’re totally on the right lines. If you see a zero at the end, you know 2 and 5 are factors. However it’s always safest with a big number like 12,500 to actually go through the process. When you do the division and explore the number like I’m showing, you discover the prime factorization is 2x2x5x5x5x5x5. 🤗😃🤩💕
Hi David, I believe on the Kumon program, they don't explain and this is a policy. The student has to get it by reading the texts and just slogging through the work. I am very glad to be able to explain in a way that makes sense and gives you the boost you need. Thanks for your note.
It's my pleasure! Once you've done a few like this, you'll be in the swing of the method. Then I want you to think about this as well; you can COMBINE methods! So when your teacher gives you a great big number, like I had here, chop it down to size using short division, then the moment you get to an answer you can solve instantly... for example 96, you just jump into 'factor tree mode'. Show that 96 is from 8 x12. 8 is from 2x4, 4 is from 2x2, and 12 is from 2x6, 6 is from 2 x3. Always remember to circle every prime, then just collect them all. This combined approach lets you finish the job quickly and effectively. Enjoy your mega-math power with this nifty strategy!
Thank you Mrs @LadyDMcollector for this video, is there any video explaining all the rules of divisibility for smaller primes, thanks a lot for your efforts and keep this up!
Hi there! You're welcome. I love this method for prime factorization - it'll whittle down to size the big numbers your teachers might throw at you without you struggling with a factor tree. On my channel, I do have videos for rules of divisibility of 2 , 3 and 5. I didn't make a video for 7, but you saw me refer to the rule for 7 in this film. Being able to spot whether 2, 3 and 5 are factors just by looking at them is an essential math skill. Generally, the numbers you'll get in school will be divisible by smaller primes (2,3,5,7,11). I ALWAYS go for the values I can spot instantly, and that means using smaller primes. 2 is very often a repeated prime, and 3. When you carve into a 3-digit+ number, then you might start to see numbers you know from your tables, like 121 which is from 11x11, both prime. Here are the links to my rules of divisibility films if you want to look at those: Rule for 2 (ua-cam.com/users/edit?o=U&video_id=kgAk6f1zenY&feature=vm) Rule for 3 ua-cam.com/users/edit?o=U&video_id=xdunx3IbkeI&feature=vm Rule for 5 ua-cam.com/users/edit?o=U&video_id=8uzNMMxuXOw&feature=vm The rules for 2 and 5 are both aimed at younger audiences. When you start to use an algorithm for division, then you can access this rule and make sense of it. I want all young kids to learn that you can spot this, then it doesn't seem like some great revelation later on when they are doing prime factorizations, because then, there's a bunch of rules to take on-board. Better to do it a little bit at a time. I hope that helps.
Thank you Mrs @LadyDMcollector for your quick answer, I am GRE candidate brushing up on my math skills, so I need to understand more the rules of divisibility for 11, 13 and up if there is, thanks a lot !
For 11, you can add, then subtract single digits in a number, and if the result is zero, or a multiple of 11, then 11 is a factor. Example: 10395 Break it into alternating positive, negative digits, left to right, then do the math: +1-0+3-9+5 = 0. Yes, 11 is a factor. 10395/11=945 The thing is, with divisibility rules for larger numbers, the rules get cumbersome and are more awkward than just pulling out your calc and trying it. I find them kind of brain-cluttering, the more convoluted they are. I don't generally give them brain-space. If I have to, I will refer to a note on this, but I retain the ones I am likely to use (2,3,5,7) For the GRE exam, are you not allowed a calculator? In the test prep for this, are you seeing questions where you are thrown a large number and required to state whether it is divisible by a particular prime, without a calculator or any working out paper? Do you know how to do short division? That will save you a ton of time on a question like this!
We have an on screen calculator and a scratch paper but we are advised to not use them and to do more mental maths because of the limited time for each question. I am at my first prep days and I'm not sure whether or not we'll have those type of question during the test but I am encountering three digits prime factorization questions in my prep book, so I am looking for shortcuts that can help me save time
3 digit prime factorization should be ok. Use whichever method you find easiest to extract primes. For myself, if I spot the value in my tables knowledge, I have an 'in', so I'll do a factor tree. If not, it's repeated short division. I ALWAYS go for the obvious small prime divisors first, and I use them till they are exhausted. Why divide by 13 if you don't have to? Check out the multiples of 13: 26 (div by 2), 39 (div by 3) 52 (div by 2), 65 (5), 78 (2), 91 is the first one you actually have to divide by 13. My advice on prime factorization is to have a crack at some for maybe half an hour, settle on your method and apply it rigorously. And do like I do...ALWAYS use those smallest primes first. I don't advise you to learn divisibility rules for 13, 17 or 19, as I expect you will chop down your number with smaller primes and then when you can't go any further, instead of doing a mathematical dance of convolution (and possibly mistake-making), when you get numbers that don't fit, you USE that on-screen calc and quickly try - is it divisible by 13? 17, 19, 23, 29? Seriously... don't get clutterbrain trying to cram this stuff. Use your noggin and time wisely and go for the fastest approach. Best, Ginny
And for four digits you need to go to 97. For five digits you need to go beyond what I have memorized. (A little Google play - you need to go to 313 for five digits.)
I don't feel it necessary to go in order. I feel students should go where their brains show them the intuitive path. If I have a value ending in 5 I'm totally going for 5, and not scratching around to see if 3 is a factor. Intuitive flair from knowing divisibility rules and 5 is faster to spot than 3.
Short division will get you there as I doubt they will give you really big numbers. But for speed, get it to where you recognize a value in your tables knowledge then switch to factor tree because it is quicker. Less marks on the page and more fluidity of the thinking.
That’s mean. Don’t take it to heart. You have come looking for help and in my thinking, that makes you a GOOD student. One who understands maybe they haven’t got it YET, but will keep on going til they do. Exactly the kind of student who makes teaching all worthwhile. That moment when a student shows they’ve got past the math roadblock is one of the most energizing I’ve ever had as a teacher. So the next step, now that you are feeling more confident, is a good amount of practice and checking your work is right until you feel like ‘I’ve GOT this!’ I ❤️ your perseverance! Never lose this awesomeness that you are showing right now. 😃🤗🥰💕
You're a wonderful teacher! This video has helped me with what I couldn't learn over the course of 3 days, I'm subscribing to your channel and look forward to more of your videos ! Thank you..
Thank you very much! I’m so happy you get this now. If you want to really get impressive with your prime factorization, you can combine the division method here... with the factor tree. As soon as you hit a number whose factors you know... let’s say you get 81 as the answer when you are dividing, well then you put a tree starter and say that’s from 9x9 and 9is from 3x3 and suddenly you finish it in a few seconds instead of doggedly going all the way to the end with division, like I did here. I think perhaps we might need to get used to that before gaining the confidence to switch partway through the prime factorization, but it’s an option, whenever you’re ready. 🤗💕😃🤩😎
it's required to try each prime in ascending order or can one use any prime number ? exemple the number in video 76 230 is evenly divisible by 2, 3, 5, 7, and 11. it's required to pick the smallest (2) or 11 is also acceptable ?
Thankyou this helped me heaps!! Could you do a video on the square root of big numbers too that would help heaps!!☘ Or if you could explain it to me that would be great thanks so much for this video i love it
Hi Katherine. I have a couple of videos that may help: Square Numbers for Beginners, and Introducing Square Root. I haven’t done a vid on square root of big numbers because the most important understanding happens with smaller values - those in our tables knowledge. I feel that once you’ve got that understanding, when faced with bigger numbers, you’re either going to estimate the square root (I have a vid on that), or you’re going to use your calculator to find the root. I hope that makes sense and you can follow my thinking. It isn’t in my plan to make a vid on square roots of bigger numbers at this point, I’m afraid.
I am a math teacher from Egypt ....and i really enjoyed your lesson ...you are a gifted teacher...thanks
Thank you very much, Mohamad. That is very kind. It means a lot to me.
you are welcome mis LadyDMcollector ....i just said the truth ...just keep creating these amazing videos
Next one... Understanding Roman Numerals. Coming soon. Please watch for it Mohamad.
I will b wait for that .... 👍👍 thanks Maam
a little worrying that a math teacher has to watch this video LMAO i guess egypt has lower standards x)
It is using your explanation of the Rules of Divisibility that really did the trick. Thank you so much.
Glad to help. 😃🤗
Thanks very much! Tomorrow is my maths exam and I'm preparing best as I can. It'll help me, I'm in junior college, still watching this. Helpful video. 🙂
Best of luck! The best you can do now is go over your notes, read through the process on any math you found tricky and refamiliarise yourself with it, doing a couple of examples (probably from some online site like math-aids.com where you can check your answers). Prime factorization is kind of a memory-muscle thing. Once you've done enough of it, you just remember it. I doubt they'll give you numbers big enough to force the use of this method, but I like to be prepared for all eventualities. Usually the factor tree is good enough. To be honest what I do now with a big number is combine the two. So I'll divide until I can spot a value from my tables knowledge, then flick into factor-tree mode and finish it in a couple of seconds. But always circle your primes so you don't accidentally miss any. All the best for your exam tomorrow, I hope it's a walk in the park for you.
😃🤗😎🤩👍💕
Hey....! LOVE ❣️ from🤩.....India , KERALA
Thanks a lot for this trick never forget your video 🥺🥺
Hi there! Love from Canada!! 💕
Glad you like this strategy. 🤗😃
THNKS SO MUCH TOMORROW IS MY EXAM AND IT ALWAYS TOOK ME SO MUCH TIME TO FIND CUBE ROOTS BUT NOW I CAN FIND IT EASILY
I like this class easily because I am a student in Kerala
You deserve 1 Million subscribers
THANKS. That's a lovely thought. Have a fabulous day, stay safe and well.
amazing explanation, Your way of talking and teaching is really good, thanks alot
Thank you very much. You can see, using this method, there's nothing to be scared of, if your teacher gives you a really big number.
You made it so easy to understand. Thank you so much!! I appreciate people like you who take the time to help those who want to learn. Thanks again! :)
Thanks. I appreciate notes like this, from people who want to learn. I’m trying to help and it makes me happy that I have helped you. 😃🤗😎💕👍
Ur way of explaining is very nice i could explain it to my son very nicely thank u please keep making more of such videos n also make a video on data handling stay blessed
For super fast factoring I first notice the 0. So I am taking a 2 and 5 all at once. I also look to grab another 2 or 3 at the same time. In her case I'd first divide by 30 and repeat.
Also, checking divisibility by three does not require you have the total. Just skip over the 3,6, and 9 digits. In her example just add 7 and 2. As a matter of fact, while you are doing 3 do 9 at the same time. In that case skip any 9s, but you do need to see that 6 and 3 are nine, and you can group 7 and 2 to be a nine. My first division might have been a 90 in her example.
Oooh, Jim! You're a math-BEAST! I love it! I can spot them, like you, but I definitely feel more comfortable going one at a time, even though I can see what's coming next. Maybe I just need to do a bunch more (as if I have time for that!! lol).
I like to get to the point where I can spot a big one, then jump into a factor tree and finish it with a speedy flourish.
Help you SO MUCH I tried and tried and could not learn this, I am in sixth grade,we are not learning this but I just wanted to calculate third roots☺
Please do yourself a favour and just focus on nailing the prime factorization of a given number. You can get to cube roots at some point in the future.
That's awesome that you could do this! I'm in 7th grade and this video was really really helpful for me too
Glad to help! 😎🤗
Me to
bruh L is a genious I'm in university and don't know this XD
So much so so so thanks it is helpfullllll❤ I will share it 😊
i love the divisibility rule for 7: double the last digit take rest of the number all digits left of the last digit and use that to subtract your original calculation which is the last digit times two, then check to see if its a factor of 7
IT SO HELP FULL THANK YOU SO MUCH
My pleasure!
Best maths teacher
And thats what a helpful video🦋 looks like 💕
Excellent explanation with no dreary introduction or silly music.
Thanks Rupert. I want to make every second count. Glad you rate it. 😎😃
Omg, I’m gonna be tested on this soon, thank you! This helps so much! 😃
Really i appreciate u do more videos let it help everyone🎉❤
Thanks a billion times.
You’re very welcome. You can speed this method up even more... when you get to a number you know in your tables, you can switch to factor tree and finish it in seconds! There’s an example of me doing this in one of the vids Finding all the Factors of a Number Using Prime Factorization. 🤗😃😎😉💕
OK thank you I will and can pls pls pls subscribe to Grace sisters
Very helpful i have to do prime factorisation for finding square roots for very large numbers it was very helpful for me
Thanks 👍👍🤗🤗
Great! Glad to help 😎😉🤗💕
Never knew how to do this method...always did by multiplying and checking... thanku so much
Cause I started cube roots
This is going to make a big difference to you then! Great! 😃🤗😎🤩
@@LetsDoMath 😊
thank you so much! im in eight grad and I never understood this until now, I scored above 90 in my square and square roots test because of this video! thank you :)
Well done! That’s amazing! A+ grade... way to GO! 🤩🤩🤩🤗😎💕
O me too I am learning this for only this chapter and in 8
Mee too
Thanks LOVE FROM INDIA 🇮🇳❤️
Right back at you!! 😃🤗💕
Thanks a lot for the trick you gave me👍👍👍👍👍👍
My pleasure. Glad to help. :o)
I am from Germany your classes helped so much for my daughter jisio
Thank you. I am so pleased to help. 🤗🥰
Wow thank u soooooooooo much for helping me understand this.
Fantastic stuff! And if you like, you could go even faster!!!
Here's how...
Use the division strategy you learned here till you get a division answer (quotient) whose factors you know.
For example let's say you end up with an answer to your division problem as 84. That's fabulous, because from your tables knowledge, you know you get 84 from 7 x 12. So the sprint-cut here is to jump out of division and into factor tree mode, right where you are on the page. Show that 84 as being from 7 x12, and 12 is from 2x6, 6 is from 2x3. Circle ALL the primes, just as every other prime factorization you've done. List them off in ascending order, or even better, using exponent notation, and you just aced it in double-quick time! NICE!!!
@@LetsDoMath thank u soo much😊
@@salmarauf4882 it’s a pleasure to help 😃🤗
I am from India, I like your video.
Thanks very much! 😎😃🤩💕
Very good explanation in very short method
Thank you very much! This will help me in my activities.
You are welcome!
Thank you so much I'm in grade 6 it was really hard but when I watched your video it was really helpful.
EXCELLENT!
Now in this video, I'm using short division all the way down to 1. But in fact... you can go more swiftly, IF you want.
Let's say you get a big number and you've whittled it down to 144.
There's no reason to keep using the division method if you don't want. You know 144 is from 12x12, so you could just flick into factor tree mode if you want... and each 12 is from 3x4, and each 4 is from 2x2! Just make sure you DO circle all those primes at the end, and make sure you collect them ALL for your final statement.
If you switch, once you hit a number whose factors you know, you can complete the prime factorization in seconds!
Now I hope you do something REALLY cool with this knowledge and totally ACE ANY number your teacher gives you for prime factorization using this little flourish to finish off. How slick is THAT!?
I'd LOVE to see your teacher's face, when they see your understanding demonstrated on the page like that!!
It really amazing ☺️☺️☺️☺️☺️
Before seeing this l get mentle by doing prime factorization now on work l can do this easily 😆😆😆😆😆😆😆😆😆😆😆
AWESOME! Rock that math! I LOVE your comment 💕😃🤗🤩🥰😎
Sure l will rock maths
And also thank yöü for your help which you do💜💜💜
It's a great pleasure!
thanks so much it's very fast to find factors👍👍👍
Isn't it? I love this method! Takes up less space than a factor tree too.
Ok
You post in 5 year s back but I sawed in 2021great😂😂
Glad you found this! Good math technique doesn’t go out of date. 😃😉😎🤗
I like this teacher
Thanks! That’s nice. It sounds like you are a student who wants to learn - I like you too! 😃🤗😎👍💕
It's very easy trick thanku so much for your help☺☺
My pleasure! Glad to help 🤗😃😎💕
@@LetsDoMath 😃😃
Wow this is good. Thank you
Thank you it helped me a lot
That's great! Thanks for letting me know. :o)
Thank you soo much mam i really enjoy your videos...🤗
U made this one Very easy. Thank you so much.
Nice! Thanks very much. And actually you can go even faster! The moment you get an answer which you recognise from your tables knowledge, you can flick into factor tree mode and finish it in seconds!
Great job...I'm very thankful to you
My pleasure! Glad to help. 😃🤩🤗
Thank you so much for this I didn't knew how to do the reminder thing.
For an easy look at how to think your way to a remainder, take a look in my Division playlist, at the vid called Short Division with a Remainder.
I'm teaching this to a grade 3 class next week! Two of them told me they won't be able to do division (I think they've heard about LONG division), but I think they will kill it with short division. I just hope their parents don't tell them it's 'wrong' because they may never have seen it.
@@LetsDoMath Oh my god I have done division all along to find the prime factors now I can find them in matter of seconds I have mastered it thank you. May God bless you
@@acy1335 Ooooh! I LOVE this comment. How come nobody has shown you this yet? Wait... Are you saying you've been using LONG division to do this? If so... eeek! I'm surprised you're still upright! So... yeah, you can use SHORT DIVISION! You can see why it's my preferred way to divide!
After doing this vid, I made a couple of others on Finding All the Factors of a Number. In those I just went at it more naturally - the moment you hit a value whose multiples you know, you can switch to the tree method then you can nail those primes in a few seconds! That's the benefit of having a bunch of math tools in your 'toolkit', so you can pull the right one just as you need it. There's always more than one way to solve a problem. If you've only been shown a single way, I feel bad for you, it's not meant to be that way. Well, not in MY opinion anyway. 😉🤗🤩💕
What a great video😀
Thanks very much. :o)
Thanks for making it easy for me
Madam super your explanation is very understanding hatsaf mam
You are too good
Thanks very much, I’m happy to help. 🤗
Thank you sooooo much ma'am this is going to help me sooo much!!!!!
That's GREAT! It may well be that you never get a big number in an exam, but if you do, you're not going to sweat, because you have a strategy! You know multiple ways to do a prime factorization and that is ALWAYS stronger than just 1. Good for you!!
Oh God I just loved it THANKS it's gonna save my 20 minutes which I used to put in my whole exercise whose actual time taking is 5 minutes!! Great !!!!
I'VE SUBSCRIBED YOUR CHANNEL ONLY AT THE BASES OF THIS VIDEO HOPEFULLY I THINK IT'S GONNA BE USEFUL FOR SURE AND ONCE AGAIN THANK U SO MUCH😊
Hi there. Glad this vid helped you. Once you've got your head around this, you can speed up even more! When you hit a quotient that you know from you tables knowledge, you can flick into 'factor tree mode'. For example if I got an answer of 96, I know that's the product of 8x12, so instead of writing out another division - and now those are both compound numbers, not prime, now I switch to the tree and show 8 and 12. 8 is from 2 x4, 4 is from 2x2, and I circle those 3 twos. And on the 12 side, I can say 12 is from 2x6, 6 is from 2x3. Here I circle both 2s and a 3. And I can do all that in seconds, as can you. Much faster than continuing to divide by 2 a bunch of times. Cool!
@@LetsDoMath WOW Thank you so much!!! You are a Genius 😃 Now I understood 👍👏
Glad to help. You are going to ROCK this stuff in class, homework AND tests!
Your method is awesome
Glad you like it.
This method sticks to itself the whole way through. In the vid on finding all the factors of a number using prime factorization, I get a bit more relaxed with it. The moment I get to a number that’s in our tables knowledge, I flick to factor tree mode instead and finish it in a couple of seconds. But you should do whatever feels comfortable to you, and as long as it works, and you and your teacher can understand it, it’s all good. 🤗😎🤩😉
Thx so much for makin this topic clear for me .
Now I understand .
Th. Fam ..♥️🙌
Happy to help, glad you get it now. You can combine this with the factor tree approach if you like, once you get down to a number whose factors you know. That will finish off the prime factorisation in a few seconds.
Very nicely explained, Thank You Very Much🙏
You're most welcome
Thank you so much madam from the deep of my heart
My pleasure! So glad to help. 😃🤗😎👍💕🇬🇧
Thank for helping me☺
Thanks for your note, Sunil. My pleasure to help. :o)
Wow it was so easy 🎉
Hii ma'am I am from India I really enjoyed your video and understand easily of😇😇🙏
Hi Laxmi,
Thanks for your note. I'm so glad it was easy to understand. It's good to be able to handle anything a teacher or exam can throw at you. It will give you lots of confidence, and that's ALWAYS a great thing. Good for you!
😃🥰🤩
@@LetsDoMath I am also glad because this one gets easy for me😇😇
thank u so much mam it was very helpful ,... u got a new subscriber
Sweet! Glad I could help. Have you been on my website, letsdomath.ca that will help you find what you need quickly. 😃😉😎
This blows my mind
An easier way to determine whether a number is divisible my 7:
If the last two digits of the number are in the 7 times table, it is divisible by seven.
I love the idea, but I don't think this is reliable though. I tried 456/7 (56/7=8)... Calc answer = 65.14285714. I am sorry. I wish it was right. It does work sometimes, but not always.
To be really honest, the divisibility rule for 7 is so time consuming, it's actually quicker for me to just scribble a division and check. I love how you thought about it and sent me a note. Thank you so much for that. :0)
Oh, If i was one of those 'stealing credit proud rude girls' i would say i thought of it. But sadly, i learnt it at school. Its in our textbooks, too. I think its because i study the CBSE syllabus. but thanks for the quick reply.. i thought i wouldnt get one for like, a few months. Glad to see you're still active!
I am always working on something.
On the replies front...YT is set up to send an alert when someone sends me a note. And I always respond, unless it's a rude one, and those I just chuck, because who needs that sort of negativity? The thing is, it has happened a few times that it didn't alert me, and then I only spot the note if I happen to check through a film's comments. Then I feel terrible because I am late answering.
So if anyone sends me a note and you don't get some kind of response, please feel free to send me another one. I don't ignore anyone.
Have a lovely day. Hope the math goes well. I am heading off to take a grade 7 math class now.
135 is not divisible by 7
Very well defined
Thanks a lot ma'am...it was sooo.... helpful
You're most welcome 😊
Thank you so much..it helped me a lot🤩
You're welcome 😊 And now I'll tell you about the 'speed-up' you can do. Instead of dividing by primes all the way down to 1, when you get to a number whose factors you know, you can jump into factor tree mode and finish in seconds! Just be sure to still circle all the primes and still gather them all up at the end! NICE!!
I study this prime factors in your chennal😁😊😊your so good at math
I’m glad if I helped you, way to go! 😃🤗🥰
😊😊
It was easy only because you choose a number with those prime factors, if a number, say 'x', is composite then it has at least one prime less then the square root of x, (x^1/2), so take for example 30623 if you tried to factor it, even supposing you knew divisibility test for a lot of primes like 13, 17, 19, 23... (i guess no one would learn divisibility for primes bigger than these) you would still not be able to factor the example that i gave you because you had to check all the primes up to 174, (in fact 30623 is actually 113*271)
It's okay that you show a way to factor MOST 5 digit numbers, but a side note on why this doesn't always work would've made the video more useful for the viewers
This is an interesting comment. The process worked easily because I created the number by multiplying up my chosen primes, then I just chose my logical order to extract the primes. I think this is a reasonable thing to do, since at up to grade 8, I don't expect ANY teacher would give an example like the one you came up with. Please remember that this channel is about giving students the power and confidence to do the math, not about showing them that it could possibly be super-tricky and you may find it stumps you completely. They've had enough of that experience already, by the time they find me.
The hardest school example I'd expect to be given would end up delivering a prime such as 41, or 59 (a prime under 100 in any case) at the end of the division sequence, and students would be expected to spot that as a prime, not know its divisibility rules.
I only ever show what I feel is needed in a video to get students revved up to have a crack - none of my videos is about running to a certain time (my kids tell me 10 minutes is the magic UA-cam earning length). Only what you need, and enough examples so I think students will get the approach and be ready to roll.
Thanks for sending me your note. :o)
LadyDMcollector Thanks for clarifying, I tought I could "add" some insight for the ones who have no trouble on this topic, I didn't want to show how It can get tricky, rather I think too many students just learn to do things mechanically without understanding the essence of It... Anyway, thanks for the kind response! :)
Awesome reply. Loved it! Have a wonderful day. :o)
I answered this before I saw your comment, but I said basically the same thing. I don't think you'd ever be asked to factor a number like 30623 on a test, but it's good to know how. And it's a MASSIVE amount of work if you're doing it mentally. If you are allowed to use a calculator, it would be very easy because you could divide 30623 by 3, 7, 11, 13, and so on and simply see if the answer comes out even. You would have to have the primes memorized up to 173 in this case. If you didn't, then you'd have to divide by EVERY number ending in 1, 3, 7, or 9 (because those COULD be primes), and it would take longer.
@@jeffw1267 yeah for sure no teacher would "trick" you with such question, but nevertheless no matter how I try I cannot single-handedly improve my school, thus I'd like other resources (such as internet) to provide something more for who Is willing to learn "one step further" my comment was just aimed at giving intuition towards the concept that prime numbers are like "Building blocks" for Natural numbers, (Check "fundemental theorem of arithmetic" for more details), primes are beautyful just like maths in general, there's no such thing as ugly maths but it's teachers fault whom just want you to know that "A Is true", or "Given this follow this pattern of steps and you complete the exercise", good job now you can exit school with your sufficiently high grade having your brain programmed to be able to do those things (until you don't forget them of course), they spend more time forcing the students to learn something than they do motivating the students to study in the first place, Sorry for the very long comment, didn't want to be missunderstood... Greetings ^_^
I can see now why divisible method of composite numbers is pretty useful at larger numbers.
One more easy trick
If you see zeros then cut the number of zeros and add the 2^n*5^n in it's factor.
See the below example to understand
for ex:- 12500 then two factors will be (2^2)*(5*2) { 2 because there are two zeros}
then it becomes 125 which is 5^3 .
So all factors will be 2^2 * 5^5
You’re totally on the right lines. If you see a zero at the end, you know 2 and 5 are factors. However it’s always safest with a big number like 12,500 to actually go through the process. When you do the division and explore the number like I’m showing, you discover the prime factorization is 2x2x5x5x5x5x5. 🤗😃🤩💕
You made it very easy
Glad to help 😃
it's very helpful for me now
Thank you mam you explain best
Thank you very much.
My pleasure! Glad to help 🤗😃😎🤩
Thanks to telling easy way
It's my pleasure to help, Purnima. Thanks so much for your note.
Thx so much, I'm in this program called kumon and their not very good at explaining. This is very helpful
Hi David, I believe on the Kumon program, they don't explain and this is a policy. The student has to get it by reading the texts and just slogging through the work. I am very glad to be able to explain in a way that makes sense and gives you the boost you need. Thanks for your note.
what abot 126053 you would thinks its prime but its factors are 233 and 541 . this is a problem i've face in my exams
Very helpful
Love u maam.
❤
Never thought i'd ever use 7 divisiblility test ever in my life.
You could just guess and check, but where’s the fun in that?
Thank You so much :)❤️
It's my pleasure! Once you've done a few like this, you'll be in the swing of the method. Then I want you to think about this as well; you can COMBINE methods!
So when your teacher gives you a great big number, like I had here, chop it down to size using short division, then the moment you get to an answer you can solve instantly... for example 96, you just jump into 'factor tree mode'. Show that 96 is from 8 x12. 8 is from 2x4, 4 is from 2x2, and 12 is from 2x6, 6 is from 2 x3.
Always remember to circle every prime, then just collect them all. This combined approach lets you finish the job quickly and effectively. Enjoy your mega-math power with this nifty strategy!
cool, thanks Ma'am
You're welcome, Sky Dragon. Are you blazing fast with this stuff now?
LadyDMcollector yes ma'am
Thanks a lot
You're very welcome. :o)
Thank you Mrs @LadyDMcollector for this video, is there any video explaining all the rules of divisibility for smaller primes, thanks a lot for your efforts and keep this up!
Hi there! You're welcome. I love this method for prime factorization - it'll whittle down to size the big numbers your teachers might throw at you without you struggling with a factor tree.
On my channel, I do have videos for rules of divisibility of 2 , 3 and 5. I didn't make a video for 7, but you saw me refer to the rule for 7 in this film.
Being able to spot whether 2, 3 and 5 are factors just by looking at them is an essential math skill. Generally, the numbers you'll get in school will be divisible by smaller primes (2,3,5,7,11).
I ALWAYS go for the values I can spot instantly, and that means using smaller primes. 2 is very often a repeated prime, and 3. When you carve into a 3-digit+ number, then you might start to see numbers you know from your tables, like 121 which is from 11x11, both prime.
Here are the links to my rules of divisibility films if you want to look at those:
Rule for 2
(ua-cam.com/users/edit?o=U&video_id=kgAk6f1zenY&feature=vm)
Rule for 3
ua-cam.com/users/edit?o=U&video_id=xdunx3IbkeI&feature=vm
Rule for 5
ua-cam.com/users/edit?o=U&video_id=8uzNMMxuXOw&feature=vm
The rules for 2 and 5 are both aimed at younger audiences. When you start to use an algorithm for division, then you can access this rule and make sense of it.
I want all young kids to learn that you can spot this, then it doesn't seem like some great revelation later on when they are doing prime factorizations, because then, there's a bunch of rules to take on-board. Better to do it a little bit at a time.
I hope that helps.
Thank you Mrs @LadyDMcollector for your quick answer, I am GRE candidate brushing up on my math skills, so I need to understand more the rules of divisibility for 11, 13 and up if there is, thanks a lot !
For 11, you can add, then subtract single digits in a number, and if the result is zero, or a multiple of 11, then 11 is a factor.
Example: 10395
Break it into alternating positive, negative digits, left to right, then do the math:
+1-0+3-9+5 = 0. Yes, 11 is a factor.
10395/11=945
The thing is, with divisibility rules for larger numbers, the rules get cumbersome and are more awkward than just pulling out your calc and trying it. I find them kind of brain-cluttering, the more convoluted they are. I don't generally give them brain-space. If I have to, I will refer to a note on this, but I retain the ones I am likely to use (2,3,5,7)
For the GRE exam, are you not allowed a calculator?
In the test prep for this, are you seeing questions where you are thrown a large number and required to state whether it is divisible by a particular prime, without a calculator or any working out paper?
Do you know how to do short division? That will save you a ton of time on a question like this!
We have an on screen calculator and a scratch paper but we are advised to not use them and to do more mental maths because of the limited time for each question. I am at my first prep days and I'm not sure whether or not we'll have those type of question during the test but I am encountering three digits prime factorization questions in my prep book, so I am looking for shortcuts that can help me save time
3 digit prime factorization should be ok. Use whichever method you find easiest to extract primes. For myself, if I spot the value in my tables knowledge, I have an 'in', so I'll do a factor tree. If not, it's repeated short division. I ALWAYS go for the obvious small prime divisors first, and I use them till they are exhausted. Why divide by 13 if you don't have to?
Check out the multiples of 13: 26 (div by 2), 39 (div by 3) 52 (div by 2), 65 (5), 78 (2), 91 is the first one you actually have to divide by 13.
My advice on prime factorization is to have a crack at some for maybe half an hour, settle on your method and apply it rigorously. And do like I do...ALWAYS use those smallest primes first.
I don't advise you to learn divisibility rules for 13, 17 or 19, as I expect you will chop down your number with smaller primes and then when you can't go any further, instead of doing a mathematical dance of convolution (and possibly mistake-making), when you get numbers that don't fit, you USE that on-screen calc and quickly try - is it divisible by 13? 17, 19, 23, 29? Seriously... don't get clutterbrain trying to cram this stuff. Use your noggin and time wisely and go for the fastest approach.
Best,
Ginny
Thanks s lot of mam really🙂🙂
My pleasure to help. 🤩🤗😃😎
thanku ma'am easy trik ke Liye thanku thanku thanku maam
Great, Suman! I am so happy you got it!
thank you so so much
My pleasure 🤩😃😎
THANK YOU
For basic learners I'd prefer to do them in order: 2,3,5,7,11,13..97. (She does 5 before 3.)
And for four digits you need to go to 97. For five digits you need to go beyond what I have memorized. (A little Google play - you need to go to 313 for five digits.)
I don't feel it necessary to go in order. I feel students should go where their brains show them the intuitive path. If I have a value ending in 5 I'm totally going for 5, and not scratching around to see if 3 is a factor. Intuitive flair from knowing divisibility rules and 5 is faster to spot than 3.
I love the way to make the concept understand to students
My pleasure to help. Thanks for your note. :o)
Thank you! Always struggle with getting this process under 60 seconds for the GRE. Need some work on my end.
Short division will get you there as I doubt they will give you really big numbers. But for speed, get it to where you recognize a value in your tables knowledge then switch to factor tree because it is quicker. Less marks on the page and more fluidity of the thinking.
Thank u so much😊😊
Im sad they sayi m bad at studies when im not. Thanks mam 😀
That’s mean.
Don’t take it to heart. You have come looking for help and in my thinking, that makes you a GOOD student. One who understands maybe they haven’t got it YET, but will keep on going til they do. Exactly the kind of student who makes teaching all worthwhile.
That moment when a student shows they’ve got past the math roadblock is one of the most energizing I’ve ever had as a teacher.
So the next step, now that you are feeling more confident, is a good amount of practice and checking your work is right until you feel like ‘I’ve GOT this!’
I ❤️ your perseverance! Never lose this awesomeness that you are showing right now.
😃🤗🥰💕
I ❤ your class
😍 thanks
😃🤗👍😉😎
Thankuuuuuu so muchhhhhhhhhhhhhhh😂🤧💜💜🤧🤧🤧🤧🤧
It’s my pleasure! 😃🤗🥰
@@LetsDoMath 💜💜💞
You're a wonderful teacher! This video has helped me with what I couldn't learn over the course of 3 days, I'm subscribing to your channel and look forward to more of your videos ! Thank you..
Thank you very much! I’m so happy you get this now. If you want to really get impressive with your prime factorization, you can combine the division method here... with the factor tree. As soon as you hit a number whose factors you know... let’s say you get 81 as the answer when you are dividing, well then you put a tree starter and say that’s from 9x9 and 9is from 3x3 and suddenly you finish it in a few seconds instead of doggedly going all the way to the end with division, like I did here.
I think perhaps we might need to get used to that before gaining the confidence to switch partway through the prime factorization, but it’s an option, whenever you’re ready. 🤗💕😃🤩😎
Does it works for all digit numbers
yes it does work for all digits
very helpful ty
Glad it helped 😉😃😎
Tq I understood 🙌
GREAT STUFF! Well done! 🤗😎😉🤩💕
Lovely video
Thank you. 😃💕
it's required to try each prime in ascending order or can one use any prime number ?
exemple the number in video 76 230 is evenly divisible by 2, 3, 5, 7, and 11. it's required to pick the smallest (2) or 11 is also acceptable ?
@Let's Do Math
Can you make a video for Prime Factorization for 6 digits?
Nah, I’ve covered this enough. You can extrapolate from here. 😉
Thankyou this helped me heaps!! Could you do a video on the square root of big numbers too that would help heaps!!☘
Or if you could explain it to me that would be great thanks so much for this video i love it
Hi Katherine. I have a couple of videos that may help: Square Numbers for Beginners, and Introducing Square Root.
I haven’t done a vid on square root of big numbers because the most important understanding happens with smaller values - those in our tables knowledge. I feel that once you’ve got that understanding, when faced with bigger numbers, you’re either going to estimate the square root (I have a vid on that), or you’re going to use your calculator to find the root. I hope that makes sense and you can follow my thinking. It isn’t in my plan to make a vid on square roots of bigger numbers at this point, I’m afraid.